Since antiviral activity of an endotoxin-affinity polypeptide separated from horseshoe crab (Tachypleus genus, Limulus genus and Carcinoscopius genus) has been found out (Japanese Provisional Patent Publication No. 2-167230 and Japanese PCT Provisional Patent Publication No. 2-500194), many attempts to synthesize novel antiviral polypeptides have been carried out by chemical modification thereof, reducing a molecular weight thereof and modifying a part of the structure of the above-mentioned polypeptide (WO92/04374, Japanese Provisional Patent Publication No. 5-163298 and Japanese PCT Provisional Patent Publication No. 8-504837). In recent years, it has been found out that novel low molecular weight antiviral polypeptides T134 and T140 are polypeptides having low cytotoxicity and having excellent anti-HIV virus activity (H. Tamamura et. al.; Biochemical and Biophysical Research Commun., 253, 877-882 (1998)). However, these T134 and T140 were not practical for a medical use.
Accordingly, an object of the present invention is to provide a polypeptide having excellent anti-HIV virus activity and low cytotoxicity.
The present inventor has earnestly carried out studies to solve the above-mentioned problems. As a result, he has found out that a novel polypeptide shows an excellent anti-HIV virus activity and has low cytotoxicity, in which a part of amino acids of T140, which has conventionally been known to inhibit infection of HIV by specifically binding to a CXCR4 ligand, is substituted with other amino acids, whereby he has accomplished the present invention.